class_docstr: Tests the `BleuMetricSpec`
code: def test_bleu(self):
      metric_spec = BleuMetricSpec({})
      return self._test_metric_spec(
          metric_spec=metric_spec,
          hyps=["A B C D E F", "A B C D E F"],
          refs=["A B C D E F", "A B A D E F"],
          expected_scores=[100.0, 69.19],
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import numpy
  import tensorflow
  from seq2seq.metrics import bleu
  from seq2seq.metrics import rouge
  from seq2seq.metrics.metric_specs import BleuMetricSpec
  from seq2seq.metrics.metric_specs import RougeMetricSpec
label_desc: Use image node_id 1 for calling the TestBleuMetricSpec obj's underlying member method code with example usage: obj.test_bleu() and returns: self